This invention relates generally to an electrophotographic printing machine, and more particularly concerns a registration system for registering substrates along a predetermined path.
A typical electrophotographic printing machine utilized in the business office environment contains stacks of cut sheets of paper or other substrates on which copies of original documents are reproduced. Generally, these cut sheets of paper advance through the printing machine, one sheet at a time for suitable processing therein. Frequently, forwarding rollers are employed throughout the printing machine for moving the cut sheets of paper along a predetermined path. In many instances, it is necessary to have the cut sheet of paper wait prior to being advanced to the next processing station by the forwarding roller so as to be in synchronism with the various processing stations in the printing machine. This may be achieved by driving the sheets against a registration gate and de-energizing the forwarding rollers so that the copy sheet waits for a specified duration of time prior to continuing its advance. Various methods have been devised for deenergizing the forwarding rollers. For example, the forwarding rollers may be spaced from one another by the actuation of a solenoid. Alternatively, the forwarding rollers may be de-coupled from the drive motor through a clutch mechanism. Also, registration gates have been bulky and non-responsive to prompt movement required by high speed printers. All of these techniques require complex linkages, are slow in movement and require high power. In addition, they introduce added expenses in building and operating the printing machine. In addition, they are inadequate for high speed printing machines. As an improvement, this sytem over other registration systems takes positive control of the paper at the exact instance the timing sequence for synchronizing an image with a copy sheet is triggered. Existing systems have uncontrolled, unpredictable variable time periods between the starting of the timing sequence and positive paper control. To solve the problems, dual voice coil actuator assemblies are provided placed side by side and simultaneously actuated in order to avoid skew. Repeatability of finger movement in present systems is about .+-.10 milliseconds, however, the present invention provides repeatability of approximately .+-.1 millisecond.